1.Regressive tax- A regressive tax ia defined as a uniformaly tax which applied on each and every individual is same. regressive tax is equally taking a larger percentage of income from low income earners. Example - goods and services tax(gst), sales taxes, user fees, property taxes, etc. These taxes applied to each individual at a same rate of percentage.

Progressive tax- progressive tax is that tax which increases as taxable amonunt increases. It charger more tax on high income and charge less tax tax on lesser income Individual. It is done to help lower-income families pay for basic shelter, food, and transportation. This tax doesn't hurt wealthy as much because even after they can afford the basics. In u.s  the income tax is progressive. Obamacare taxes are progressive. the estate tax is progessive.

Regressive tax and is uniformal tax which charge same wheather individual income level is high or low. On the other hand, progressive tax is charge as per income level it increase as income level high. based on these definations, a tax on prescription drugs would most likely to be a regressive tax, since prescription drugs sre sold in pharmacies where it wouod be easy to add taxes on individual sales. It should also consider that why these taxes to be implemented in the first place. Government would levy taxes on prescription drugs. taxes on alcohol and cigarettes have been passed in an attempt to discourage their consumption. regressive tax on consumption drugs will lead to discourage its consumption too because it is harmful for individual to consumption of alcohol and cigarettes. Taxes on harmful products would imposed regressive tax which are equal to everyone.

2.Please use this google drive link to download the answer file.       

https://drive.google.com/file/d/1ElIVaAnpX0COPzXUZmMq8K3gqMEPNsiR/view?usp=sharing

Note: If you have any trouble in viewing/downloading the answer from the given link, please use this below guide to understand the whole process. 

https://helpinhomework.org/blog/how-to-obtain-answer-through-google-drive-link \

3.

In the above mentioned question,

Student 1(s1) prefers School B,

also,

School B prefers Student 1(s1)

So, ( s1, B) is efficiently allocated referring to both preferences.

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In the 2nd case,

Student 2(s2) prefers School D

but,

School D prefers Student 3(s3)

So, (s2, D) is not a stable and efficient allocation.

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In 3rd case,

Student 3 ??????(s3) prefers School A

but,

School A prefers Student 2(s2)

So, (s3, C) is not a stable and efficient allocation.

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In the 4th case,

Student 4(s4) prefers School D,

but,

School D prefers Student 3(s3)

So, (s4, A) is not a stable and efficient allocation.

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Therefore we can conclude that in this whole allocation only (s1, B) is perfectly stable and efficient allocation.